This progress report broadly defines the scope of supplementation plans and activities in the Columbia Basin. It provides the foundation for more detailed analysis of supplementation in subsequent reports in this series. Topics included in this report are: definition of supplementation, project diversity, objectives and performance standards, uncertainties and theory. Since this is a progress report, the content is subject to modification with new information. The supplementation theory will continue to evolve throughout the duration of RASP and beyond. The other topics in this report are essentially complete and are not expected to change significantly. This is the first of a series of four reports which will summarize information contained in the larger, RASP progress and completion reports. Our goal is to make the findings of RASP more accessible by grouping related topics into smaller but complete narratives on important aspects of supplementation. We are planning to publish the following reports under the general title Supplementation in the Columbia River Basin: Part 1, Background, Description, Performance Measures, Uncertainty and Theory; Part 2, Theoretical Framework and Models; Part 3, Planning Guidelines; and Part 4, Regional Coordination of Research and Monitoring. Supplementation is expected to be a major contributor to the planned increase in salmon and steelhead production in the Columbia Basin. The Fish and Wildlife Program of the Northwest Power Planning Council (NPPC) uses three approaches to protect and enhance salmon and steelhead in the Columbia Basin: (1) enhance fish production; (2) improve passage in the mainstem rivers; and (3) revise harvest management to support the rebuilding of fish runs (NPPC 1987). The fish production segment calls for a three-part approach focused on natural production, hatchery production, and supplementation. Supplementation is planned to provide over half of the total production increases. The Regional Assessment of Supplementation Project (RASP) was initiated as a result of a request by NPPC to address long-standing concerns about the need to coordinate supplementation research, monitoring and evaluation. Such coordination was also recommended by the Supplementation Technical Work Group. In August 1990, the NPPC gave conditional approval to proceed with the final design of the Yakima Production Project. The Council called on the Bonneville Power Administration (BPA) to fund immediately a supplementation assessment to reevaluate, prioritize and coordinate all existing and planned supplementation monitoring and evaluation activities in the basin. Providing for the participation of the fishery agencies and tribes and others having expertise in this area. RASP addresses four principal objectives: (1) provide an overview of ongoing and planned supplementation activities and identify critical uncertainties associated with supplementation, (2) construct a conceptual framework and model which estimates the potential benefits and risks of supplementation and prioritizes uncertainties, (3) provide guidelines for the development of supplementation projects, (4) develop a plan for regional coordination of research and monitoring. These objectives, once attained, will provide the technical tools fishery managers need to carry out the Council's direction to protect and enhance salmon and steelhead. RASP has further divided the four broad objectives into 12 technical topics: (1) definition of supplementation; (2) description of the diversity of supplementation projects; (3) objectives and performance standards; (4) identification of uncertainties; (5) supplementation theory; (6) development of a conceptual model of supplemented populations; (7) development of spreadsheet model of risks and benefits of supplementation; (8) classification of stocks, streams, and supplementation strategies; (9) regional design of supplementation evaluation and monitoring; (10) guidelines for planning supplementation projects (11) application of the spreadsheet model to supplementation planning; and (12) experimental design and decision making with uncertainty.